docs: def rectwidth(self):
          """Calculate :ref:`pysynphot-formula-rectw`.
  
          Returns
          -------
          ans : float
              Bandpass rectangular width.
  
          """
          mywaveunits = self.waveunits.name
          self.convert('angstroms')
  
          wave = self.wave
          thru = self.throughput
          self.convert(mywaveunits)
  
          num = self.trapezoidIntegration(wave, thru)
          den = thru.max()
  
          if 0.0 in (num, den):
              return 0.0
          else:
              return num/den